Hydraulic control system



Feb. 24, 1953 T. c. RUSCONI 2,629,306

HYDRAULIC CONTROL SYSTEM Filed July 15, 1949 2 SHEETS-SHEET 2 v INVENTOR- THEODORE C. Ruscom TTO RNEYS i 'atented Feb. 24, 195 3 UNITED STATES PATENT OFFICE HYDRAULIC CONTROL SYSTEM Theodore C. Rusconi, Sanger, Calif.

Application July 15, 1949, Serial No. 104,874

1 '7 Claims. The'present invention relates to control systems for agricultural implementsand more par ticularly to a hydraulic control system operable in connection with a draft appliance having an elevationally positionable tool bar tociiect automatic elevational positioning of the tool bar in response to resistance offered toiorward movement of the draft appliance. a

Tractors providing" elevationally positionable tool bars for mounting earth working tools have become well known and popular, particularly for relatively light cultivation requirements as experienced in the tilling of truck gardena vineyards, orchards, and elsewhere where the earth working tool desired to be employed is suitable for direct tractor mounting of plows, cultivators, discs, and the like directly on the tool barsof such tractors has proved or" great aid, it hasbcen subject to certain difficulties which the present invention seeks to overcome. l

Such tool bars are usually elevation'ally pcsitinned by a hydraulic ram. The operational height of the tool bar is predetermined byproliminary adjustments prior to operation. Varied soil character, varied moisturecontent, and uneven terrain causes earth working tools borne by such tool bars 'to enga-ge the. earth to various depths and to impose widelyvaried resistances to forward movement of the tractor. Frequently mounting. Although the a tractor in response to a given throttle setting.

tools home by such tool bars'rearwardly of tractors tend to depress the 'rearward cnd of the tractor upon increased load and such depressingiurther to increase the load by greaterfidepth of soil engagement, necessitating frequent interruption of the cultivating operation to readjust the tool bar position. i

i In an unsuccessful eilort to solve these prob:- lems', many such tractors have been provided with governors which automatically increase the fuel supply to the engines thereof in response to decrease. in motor speed...incident to the excessive drag imposed by an earth working tool. This arrangement has been found :to impose undue strains on the 'tractonon the earth working tool,

Another object is to provide improved 618'? ments and arrangements thereof in a device Of the character and for the purposes set forth.

Further objects willbecome apparent in the. subsequent description in the specification.

. Inthe drawings: V.

1 is a side elevational View of tractor having a rear wheel removed for convenience in illustrating a hydraulically controlled elevation 1 allypositionable tool bar mounte on the tractor and controlled, by the apparatus of the invention. v

Fig. 2 is a, diagrammatic representation of the hydraulic control apparatus the present in ventionincluding in lon itudinal section a valve structure employed therein as positioned to lock the elevationally positionable tool bar in adjusted po t o -H I r Fig. 3 is a view of the elements shown in Fig. 2 demonstrating the positioning of the valveto modiiy the elevational positioning of the tool bar. Referring in greater detail to thedrawing si in Fig 1 illustrated a tractor it which ex emplifics draft appliances with which the. con;

present trol apparatus of the present invention. is adapted to be used. The tractor is supported for ground traversing movement on steerable front wheels ii and power driven rear wheels I2. The rear wheels are driven by an engine it provided with controlled amounts or" operating fuel through an and to result in such widely varied earthwork- .7

ing results as to be objectionable. Still further, the mere increase of fuel supply to the engine oithe tractor coining afterthe imposition of an excessive load thereon does not necessarily en;- able the engine to increase its speed and thus its power in response to increased fuel and a substantial fuel loss isexperienced. i An object of the present invention is, therefore, to provide in a draft appliance an improved control system .ior an elevational-ly positionable tool :bar. I

Another object is to 'translate the dragof-an earthworking tool mountedon anuelevationally positionable tool bar-ore draft appliance: into ing 'outer ends pivotallyconnected to can-nectarintake manifold M and conneo ted carburetor i in the conventional manner. i

A tool bar Sills supported and elevationally positionable in any convenient manner on a pair of links it pivotedto the tractor and the new; bar

drawbar is adaptedto support one or n oresoi H A line implements, such as a plow, disc harrow or the like} A second pair oflinks ,Ztar'e pivoted'ior vertical movement on the tractor havlbars .2;! which v turn. are pivotally attached, at thei lo -'er ends; to the outer endsof the links Qn vetical pivotal movement ofthe links t9 1 and 2t, thetool bar it' and implements (not shown) mounted thereon are jelevationally positioned in response thereto. ,The tractor and tool bar mounting, as thus far described, is of generally we llsnm n. ns u tion .iree erai yans pe rlessh W h it a 3 hydraulic ram 22 having a piston rod 23 extended therefrom is pivotally connected to the outer free ends of the links 23. The ram has 'a conduit25 connected to its lower end adapted to service the ram with hydraulic fluid under pressure to extend the same. Another conduit 26 is connected in fluid communication with the upper end of the hydraulic ram and is adapted to contract the ram to lower the drawbar when hydraulic pressure is applied to the ram therethrough. As is the conventional practice, when pressure is supplied to one of the conduits fluid is bled from the opposite end of the ram through the other conduit.

The tool bar mounting structure, the type of ram shown, and the arrangement of the mounting and the ram are essentially conventional and illustrated to facilitate description of the system of the present invention. It is to be understood that the present invention is not limited to use with the specific ram and tool bar structure and association described but may suitably be employed with any elevationally positionable tool bar which is elevated and depressed by hydraulic means.- Further, it is possible to employ the ram on agricultural implements having adjustable depth of soil engagement or other means for regulating resistance to earth traversing movement so that the system of the present invention accomplishes the automatic regulation of draft resistance imposed upon the tractor. Such an association is believed to be within the scope and spirit of the present invention.

The carburetor I is provided with a conven tional throttle control,-not shown, and the flow of fuel to the carburetor regulated by said throttle, as modified by a governor shown generally at 30. The governor maybe of the fiy-ball type, as shown in Figs. 2 and 3 or of any other suitable form. Such governors are frequently conventional equipment on tractors and are connected by a governor-throttle control rod 3| connected to a fuel regulating butterfly, such as at 32. It is sufiicient for purposes of the present invention to observe that the governor 30 provides an arm 33 which is pivotally positioned in response to engine speed variations at any given throttle setting and to which the governor-throttle control rod 3| is connected.

As shown in Figs. 2 and 3, an electrical contact 35 is mounted on the arm 33 for unitary reciprocal positioning therewith. A pair of spaced electrical contacts 36 and 31 are mounted for engagement by the contact 35 upon pivotal movement from its normally central position. The contacts 36 and 31 are preferably arcuate in form and arranged so that the contact 35 can pass thereacross without inhibiting governor operation while establishing electrical contact with either thereof. If desired, the contacts 36 and 31 may be mounted for adjustable spacing relative to the normal operating position for the contact 35 so as to adjust the acuity of operathe right or to the left will continue the electrical engagement between the contact 35 and the appropriate contact 36 or 31.

As will subsequently become apparent, means are provided for biasing the operation of the governor consistingof a control arm 373a pivotally mounted in. the tractor, as at 38, in a position conveniently accessible by a tractor operator and provided with a concentric toothed plate 39 in association with which a detent 40 mounted on the arm 3'la' latches the arm in operator adjusted position. The arm 31a is downwardly extended from its pivotal mounting and said downwardly extended end is connected to the arm 33 by means of a resilient linkage 4! whereby the operation of the governor may be resiliently urged through the linkage 41 in response to setting of the arm 3'ia to aid or to resist outward throw of the' balls and the resulting effects on the fuel supply to the engine l3 of the tractor.

A reservoir 45 for hydraulic fluid is provided on the tractor and a fluid pump 43 associated therewith whereby fluid under pressure is delivered to the system of the present invention. An intake line 47 interconnects the pump and the reservoir. The pump has a high pressure discharge line 48 extending therefrom. A return conduit 49 interconnects the system ofthe present invention and the reservoir for return flow of fluid to the reservoir from the system. A by-pass safety valve 53 interconnects the high pressure conduit 48 and the return conduit 49 so that any excessive pressures built up by the pump are dissipated through the valve back to the reservoir 45.

As shown in Figs. 2 and 3, a master control valve, indicated generally at 60, is interposed the conduits 25 and 26 and the conduits G8 and 49. The valve consists of a housing 6! having a cylindrical inner bore 62, a closed end portion 53, and a threaded opposite end portion 64. A core 35 is slidably fitted to the bore 32 in substantial fluid tight engagement therewith. For controlled positioning of the core 65, control rods 66 are axially and concentrically extended from the core to positions exteriorly of the engaged in the opening 34 in closing relation to the housing. It will be apparent that axial movement of either of the control rods 66 from externally of the housing 6| results in responsive positioning of the core 55 within the housing. Packing glands 68 serve to preclude leaking of fluid about the control rods. If desired, the closed end portions 63 and 3'! may be ported so that opposite end portions of the core 65 are subjected to atmospheric pressure.

The core 65 consists of a plurality of adjacent, axially aligned, concentric portions, alternate ones of which are slidably fitted to the housing 6| with intermediate portions formed of reduced diameter to define circumscribing fluid passages. A central portion of reduced diameter is provided in the core to accommodate a cir-cumscribing high pressure passage Hi about the core within the housing. The high pressure passage 10 is axially definedby a pair of spaced primary gates H slidably fitted to the housing. Endwardly adjacent the gates H are portions of reduced diameter 12 providing circumscribing control passages 73 axially limited at their outer ends by enlarged cylindrical portions 14, referred to as secondary gates, slidably fitted to the housing. Portions of reduced diameter 15 axially adiaeent: t9 the secondary gates 74 provide circumsc 'i bing fluid return passages Hi thereal oout axially limited by annular fluid retaining flanges T slidably fitted to. the housing. each have a circumscribing groove 18 which receives a packing 1.9 to preclude lealn'ng of hydraulic; fluid within the housing axially beyond the portions 51?.

pressure passa e i9 by bores 88 formed through the. primary gates i y A supply port Si is Provided centrally of the housin El for registration with the high pres.- sure passage T3 in the core 65. The supply port 9,0 is. of a size sufficient continually to register with the. high pressure passage 'h'i during all longitudinal movement of the core. The port 9!); is; connected to the pressure. supply conduit 1-8. A pair of fluid return ports 9i are provided in the, housin in longitudinally spaced. relation to the ports Qt and arranged to register with the return. passages 'lfipwhen the. core. is in central position. The return ports.@ I. are both connected.

to, the return conduit 49;. An exhaust port; 92 is, provided in alignment transversely of the housing; 6t with the; pressure; supply port 90; A pair of; return ports 9:3; are provided in the. housing transverse alignment with the, ports 91. A by-pass conduit. SM] interconnects the ports or and; both of the ports 93; Intermediate. the ex haust ports; 92- and each of. the returnports controlportsr 51 are, provided in the housing 6! in positionsblocked the secondarygates M when the core isin central position, as. shown in Fig; 2. One of. the control ports 95 is connected to the conduit. 2-5 and the other control port 95 connected to the'conduit 26.

ToeontrolthE -PQSitiOIIiHg of; thevalve core 55 in: housing 5!, solenoids indicated generally at 9,6; having windings 9i, and cores 98; arecon' nected. to the; valve core. as by screw-threaded engagement by the;- solenoid cores; with the control rods- 56. Ihe:solenoids are; -arrang edto have opposing; effects on the coreso, that, as subseq nentiy; described, energizing of one? of the: coils v ruses;the core" axially inone directionin the housing and energizing of the .oppositecoil urgesthe; core in: the, opposite direction. A mounting frame. 6.53 is; extended axially from thenhcusing; in caging; relationto the solenoids and. mounted end portions m3; traversing alignment: with: the

control rod 5.5 andwsolenoids: 9B andighave bore said elements. Asecondaryrframe Hltismount edjon: the frame. i551" and endwardly extended therefrom, providing in spacedrela-tiomto the-end. portions i or; secondary;endportions. l Bevin-which" prpvisionis made ofboresx l 1 tin axial; alignment. with'the bores Hi l;

. Stop members. i l5; are mountedgin the'hores. 1M and it, for axialslidab1e.;movementrthereein; Each-off the stop; members li5- provides a stop members; Thisqinward limit to themoyemerit; of; the; stop members: is 4: arranged so that c said step; members; abut: the adjacent; solenoid.

cores ,fiawwhen the valve core 65 {is 1 centrallyxposi tioned z as; shown. in. Fig; 2;. and; springs; H1 are provided under initial compression-ibetweengthe:'

collets H 167 and; the; secondary; end portions; I89 so that-, saidrjstop members; resilientlmi'. resist The control passages 13 are: connected in. fluid communication with the high s; ifiidyformed therein iniaxial alignment with.

' connected by a lead wire I21 to one pole of the movement of their respective solenoid coils theretoward. It is significant that thestop memhers are not connected to the solenoids and that they only resist movement of their respective A battery ifit mounted on the tractor H) con} veniently provides a source of electrical energy for selectively energizing the coils 91- of the sole noids 96. One end of each of the coils 9'1 is battery. The opposite pole of the battery is connected through a manually operated switch I22 by means of an electrical conductor I23 to the movable contact 35. The opposite ,end of one of. the coils t? is connected by an electrical 0011- ductor 24. to the fixed. contactfiii and the oppositeend of the other coil 9'! connected by an electrical conductor i25 to the contact 31. The manually operable switch 122; provides means for interrupting the electrical circuits iust olescribed so that the core 65' remains inits centered. position under the urging of the springs ill. As previously suggested, the solenoid coils 91- are arranged to have opposite positioning effects on the core 65 for displacement thereof fromthe central position: when the switch 522 is closed and upon engagementiby the contact with either of the contacts dtror 31.

Operationa The operation. and utility of the present invention is believed apparent fromthe foregoing description and is briefly summarized at this point.

1 When the. tractor ii! isgnot in operation; the manual switch IE2! is opened so that there is no drain. on the battery igfl anol noforees imposed upon the core 65. incident to energizing of the solenoid coils 557. y In the absenceef anyelectrical effects onthe solenoids, thestcp'memhers H5 under the urging of the springs HT urge the core into centralpositiomdemom strated in Fig. 2Q

When the engine l3of'tlie tractor lil isstartedi the hydraulic pump 46, which has-any suitable motivating connection torthe. engine I 3} ,is energizediand hydraulic fiizidiunderpressureis drawn passage it ut theexhaustportliizi, through the by-pass conduit 95,. back. into the housing 6i,

through the. returnports 93, through the return passagesffi, outwardly thi'oughnthe return ports 91 and by Way of the conduit-49. baclsto the reservoir. Insuclicondition, the secondary gates 'Mioverlay the controlipoi is QE and the .ram 22 is locked. in its. initial position,whatever that may be, by the blocking of the-conduits Eda-rid 25. Thus, the tractor may. beremp-loyed with the tool bar 18 locked inany given predetermined elevation by the opening ofetheswitch ln. This permits the convenient transporting of any earth working. tool, not shown, mounted on the tool bar |8. or working ofthe earth bysuch tool with the tool bar locked in a lowered position without employing the automatic elevating of thetool bar an'dearth working. tool incidentto the op eration' ofthedevice'. andsystem of the present invention; i

The: arrangement of the governor, the; governor-control arm 33+ and the'switch contacts 35;.

.duit 26.

aeaasoc 3B and 31 is such that at normal operating speeds the iiy-balls of the governor will position the movable contact 35 intermediate the fixed contacts 36 and 31. As previously described, the control arm 31a may be positioned resiliently to affect the governor operation and positioning of the contact 35 as desired. When the switch I22 is closed with the contact 35 disengaged from both of the contacts 36 and 31, there is no electrical effect on either of the solenoids and the core 65 remains in its centrally located position under the urging of the springs I [1. Also, as previously suggested, the contaots 36 and 31 may be mounted for relative special adjustment relative to the central position of the movable contact 35 to modify the acuity of operation of the system of the present invention, or may be mounted for unitary shifting movement of the contacts 36 and 31 relative to contact 35, if desired. The adjustable mounting of the contacts 36 and 31 may provide a useful adjunct to the present invention but is not considered essential to its successful operation and thus these details relating to adjustable mounting are not described in greater detail nor claimed in the instant application.

If it is assumed that the ram 22 is locked in the contracted condition with the tool bar 18 lowered and an earth Working tool borne thereby positioned in soil engagement, it will be apparent that resistance offered by the tool to forward 1 movement of the tractor l will vary in response to types of soil encountered, moisture content of the soil, and objects such as roots and the like engaged by the earth working tool. It is these variations in resistance to forward movement of the tractor that has caused the considerable difficulty already described. With the switch I212 closed, such variations result in modification of the elevation of the tool bar and thus in automatic elevation of the earth working tool so that substantially constant resistance to forward movement of the tractor is achieved.

As shown in Fig. 3, if a substantially increased resistance to the forward movement of the tractor is encountered, the engine speed of the tractor will be somewhat reduced and the fly-balls of the governor 30, due to decreased centrifugal force thereon, will lower. This pivots the governor control arm 33 in a counter-clockwise direction, as viewed, and brings the movable contact 35 into engagement with the contact 31, energizing the coil 91 of the solenoid shown at the right of the drawings. The energizing of this solenoid draws the core 98 into the coil 91 and urges the core 65 of the master control valve 613 to the left and compresses the spring H1 at the left. In this position, the primary gate 1| at the right of the high pressure passage 19 overlays the exhaust port 92 and precludes fluid movement therethrough. Fluid under pressure, admitted to the high pressure passage 19 through the supply port 99, blows to the left through the bore Bil into the control passage 13 and thence outwardly through the adjacent control port 95, into the conduit 25. The imposition of hydraulic fluid under pressure on the ram through the conduit 25 serves to extend the ram, necessitating a bleeding of fluid therefrom through the con- Fluid returning through the conduit 26 passes through the right hand control port 95, as viewed in the drawings, into the right hand return passage 16 and thence through the right to the reservoir. The extension of the ram, as

evident in Fig. 1, serves to elevate the tool bar l8, which in turn reduces the depth of earth engagement of any earth working tool borne by the tool bar, resulting in a reduction in resistance offered to forward movement of the tractor. This reduction in resistance to forward movement permits the engine l3 of the tractor to increase its speed, without throttle movement, the flyballs of the governor 36 move outwardly, and the movable contact 35 is withdrawn from engagement with the contact 31. Upon interruption of the electrical circuit of either of the solenoids, the springs H1 return the valve core 65 to central position, again locking the ram in adjusted position and permitting the by-pass of hydraulic fluid under pressure through the valve back to the reservoir.

It will further be apparent that any substantial decrease in resistance to forward movement of the tractor l0, while the switch I22 is closed, will result in outward movement of the fly-balls of the governor 36, movement of the governor control arm'33 to the left, as viewed, and engagement of the movable contact 35 with the contact 36 resulting in the energizing of the solenoid coil 91 at the left of the drawings. This will axially move the valve core 65 to the right, as viewed, resulting in an imposition by hydraulic fluid under pressure on the ram through the conduit 26 and bleeding of the opposite end of the ram back through the conduit 25 and the master control valve to the reservoir. Hydraulic fluid under pressure passing to the ram through the conduit 26 contracts the ram and forcibly lowers the tool bar 18, increasing the depth of earth engagement by any earth working tool borne thereby. The lowering of such an earth working tool automatically increases the resistance to forward movement of the tractor, resulting in a decrease in speed of the engine l3 without throttle manipulation. The decrease in engine speed results in the displacement of the contact 35 from the contact 36 and the interruption of the electrical circuit to their respective solenoid coils 91, and the valve core 65 is urged into central position by the springs H1, again locking the ram in adjusted position.

Thus, it is possible at a given throttle setting to perform an earth working operation by use of the tractor without any substantial variation in the speed of the earth traversing movement of the tractor or the power available at the tool bar. In actual operation, the system of the present invention has proved effective in automatically adjusting elevation of the tool bar to resistance offered to forward movement of the tractor. In operation, it is normal to set the throttle of the tractor to achieve the desired earth traversing speed and through adjusted setting of the control arm 31a. to bias the governor 30 through the resilient linkage 4| so that a substantially constant predetermined resistance to earth traversing movement is set and so that any substantial departures from said predetermined resistance results in the closing of an electrical circuit to either of the solenoids, modifying the elevation of the tool bar 18 in response thereto.

The ram 22 may be mounted on any desired earth working tool so that contraction and extension of the ram affect the resistance of the earth working tool to forward movement without departing from the spirit or the scope of the present invention. 7

The essence of the present invention is believed to reside in the provision of a system for trans- 'lating engine speedvariations incident to loads 'from with-in the scope of my invention, which is not to be limited to the details disclosed herein, but is to 'be accorded the full scope of the claims so as to embrace any and all equivalent devices and structures.

Having described my invention, whatI claim as new and desired to secure by Letters Patent is:

I. In combination, a tractor having an engine for motivating the tractor in earth traversing movement, a source of electrical energy, a throttle controlling fuel supply to the engine, and a source of hydraulic fluid under pressure; a tool bar mounted on the tractor for elevational movement; a two-way ram interconnecting the tractor and the tool barand elevationally positioning the tool bar by telescopic adjustment of the ram; a governor mounted on the tractor and connected to the engine; a hydraulic system interconnecting the source of fluid underpressure and opposite end portions of the ram; said system including valve means adapted to direct hydraulic fluid under pressure from the source thereof to either end or the ram while simultaneously opening the other end of the ram to bleed hydraulic fluid therefrom; electromagnetic means having controlling connection to the valve means"; an electrical circuit interconnecting the source of electrical. energy and the electro-magnetic means; anda switch in the circuit connected to the governor having an open condition in which it is positioned by the governor when the engine is operated at a predetermined speed, a tool bar lowering, condition providing an electrical path therethrough to the electro-magnetic means regulating the valve means to extend the rain in whichit is positioned by the governor when the engine speed increases beyond said predetermined speed,anda tool bar raising condition providing a second electrical path therethrough to the electro-magnetic means regulating the valve means to contract the ram in which it is positioned by the governor when the engine speed decreases below the predetermined speed.

2. The combination of a tractor having an elevationally positionable tool bar mounted thereon, a source of hydraulic fluid under pressure, an engine for motivating the tractor in earth-traversing movement, and a governor responsive to engine speed variations; a ram connected to the tool bar and to the tractor in elevation controlling relation to the toolbar; a hydraulic system interconnecting the source of hydraulic fluid under pressure and each end of the ram, said system including a master control valve having :a neutral position in which fluid flow to and from both ends of theram is blocked, a ram extending position in which fluid is fed under'pressure to one end of the ram while bleeding the opposite end of the ram, and a ram contracting position in which'fluid is fed under pressure to said opposite end of the ram while said first mentioned end of the ram is bled; resilient means urging the valve into neutral position; electromagnetic means having controlling connection source of electrical energy and the electro-magnetic means; and a switch in the circuit having a movable contact electrically connected to the source of electrical energy and having position controlling connection to the governor and a pair of spaced contacts engageable by the movable contact, one thereof being electrically connected to the electro-magnetic means whereby energizing of the electro-magnetic means therethrough positions the control valve to extend the ram and the other thereof being electrically connected to the electro-magnetic means whereby energizing of the electro-magnetic means therethrough positions the control valve to contract the ram.

3. In a tractor having an engine and a tool bar mounted for adjustable elevational movewent, a governor responsive hydraulic control system comprising a source of fluid under pressure, a two-Way ram connected betweenthe tractor and the tool bar, conduit means interconnecting the source of fluid under pressure and each end of the ram, a master control valve positioned in the conduit means andhaving a reciprocablecore adapted when centrally located to close the conduit means between the ram and the reservoir, to direct fluid under pressure to to the valve; an electrical circuit including a source or electrical energy interconnecting the one end of the ram through the conduit means while bleeding the opposite end of the ram through the valve when displaced in one direction from central position and to impart fluid under pressure to said opposite end of the ram while the first mentioned end of the ram is bled through the valve when oppositely displaced magnetic means including a pair of fixed contacts and a movable contact, said circuit being arranged with the electro-magnetic means so that the core is drawn to one position displaced from central position by engagement of. the movable contact with one of the fixed contacts and to the opposite displaced position by engagement of the movable contact with the opposite fixed contact, and speed responsive governor means connected to the tractor engine mounted in posinon-controlling relation to the movable, contact whereby variation in governor speed is translated into movement of the movable contact to and :from individual engagement with the fixed contacts.

4. A tool bar control system for tractors having at tool bar mountedfor elevational movement thereon, a source of motivating power, a throttle for controlling fuel supply to the source of motivating power, and a source of electrical energy, comprising a governor having driven connection to the source of motivating power; a contractible and extensible ram interconnecting the tool bar and the tractor for adjustable elevationa'l move- 'ment of the tool bar relative to the tractor; a source of hydraulic fluid under pressure; a conduit interconnecting the source of fluid under pressure and opposite ends of the ram; a master control valve positioned in the conduit having, a neutral position in which fluid flow to and from the ram is blocked, an elevating position in which fluid flow is directed to one endof the ram to contract the ram while bleeding fluid from the opposite end of theram, and a depressing position in which fluid flow is directed to said opposite end of the ram causing the ram to expand while bleeding fluid from the end of the ram to which fluidis directed for contracting purposes; electrical means having controlling con- .nection to the valve; and an electrical switch connected to the governor and electrically connected between the source of electrical energy on the tractor and the electrical means, said switch having a neutral position in which electrical communication between the source of electrical energy and the electrical means is interrupted,

.an elevating position in which a path of electrical current through the switch to the electrical means is provided energizes the electrical means to position the valve to contract the ram, and a depressing position in which an electrical path is established through the switch to the electrical t means energizing said electrical means to position ;the valve to expand the ram.

5. In combination, a tractor having an engine for motivating the tractor in earth traversing .movement, a source of electrical energy, a throttle controlling fuel supply to the engine, and a .source'of hydraulic fluid under pressure; a tool .bar mounted on the tractor for elevational move ment; a two-way ram interconnecting the tractor and the tool bar and elevationally positioning the tool bar by telescopic adjustment of the ram; a governor mounted on the tractor and connected to the engine; a hydraulic system interconnecting the source of fluid under pressure and opposite end portions of the ram; said system including .valve means adapted to direct hydraulic fluid under pressure from the source thereof to either end of the ram while simultaneously opening the other end of the ram to bleed hydraulic fluid therefrom; electro-magnetic means having controlling connection to the valve means; an elec 'trical circuit interconnecting the source of elecvalve meansto extend the ram in which it is positioned by the governor when the engine speed increases beyond said predetermined speed, and a tool bar raising condition providing a second electrical path therethrough to the electromagnetic means regulating the valve means to contract the ram in which it is positioned by the governor when the engine speed decreases below the predetermined speed; an adjustably positioned control lever; and resilient means interconnecting the control lever and the governor whereby operation of the governor in response to increase in engine speed is adjustably resisted.

'6. The combination of a tractor having an elevationally positionable tool bar mounted thereon, a, source of hydraulic fluid under pressure, an engine for motivating the tractor in earthtraversingmovement, and a governor responsive to engine speed variations; a ram connected to the tool bar and to the tractor in elevation controlling relation to the tool bar; a hydraulic system interconnecting the source of hydraulic fluid under pressure and each end of the ram, said system including a master control valve having a neutral position in which fluid flow to and from both ends of the ram is blocked, a ram extending position in which fluid is fed under pressure to one end of the ram while bleeding the opposite end of the ram, and a ram contracting position in which fluid is fed under pressure to said opposite'end of the ram while said first mentioned end of the ram is bled; resilient means urging "the valve into neutral position; electro-magnetic means having controlling connection to the valve; an electrical circuit including a source of electrical energy interconnecting the source of electrical energy and the electro-magnetic means; a switch in the circuit having a movable contact electrically connected to the source of electrical energy and having position controlling connection to the governor and a pair of spaced contacts engageable by the movable contact, one thereof being electrically connected to the electro-magnetic means whereby energizing of the electro-magnetic means therethrough positions the control valve to extend the ram and the other thereof being electrically connected to the electro-magnetic means whereby energizing of the electro-magnetic means therethrough positions the control valve to contract the ram; an

adjustably positioned control lever; and resilient Imeans interconnecting the control lever and the movable contact of the switch.

7. In a tractor having an engine provided with a carburetor and having a tool bar mounted for adjustable elevational movement, a governor responsive hydraulic control system comprising a source of fluid under pressure, a two-way ram connected between the tractor and the tool bar, conduit means interconnecting the source of fluid under pressure and each end of the ram, a master control valve positioned in the conduit means and having a reciprocable core adapted when centrally located to close the conduit means between the ram and the reservoir, to direct fluid under pressure to one end of the ram through the conduit means while bleeding the opposite end of the ram through the valve when displaced in one direction from central position and to impart fluid under pressure to said opposite end of the ram while the first mentioned end of the ram is bled through the valve when oppositely displaced from central position, resilient means urging the core of the valve into central position, electrical solenoids connected to opposite ends of the core in opposition to each other, an electrical circuit including a source of electrical energy including a pair of fixed contacts and a movable contact, the fixed contacts being individually connected to the solenoids and the movable contact being connected to the source of electrical energy, agovernor connected to the REFERENCES CITED The following references are of record in the file of this patent:

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